I engage the manuals in advance if I even think there is a possability that I might need 4WD like if it is raining. Engaging 4WD in the t-case while moving when it is cold is a lot easier with the hubs already engaged too. My fuel economy penalty with them engaged is less than 1/2 MPG.

Ron Schroeder
Long Island NY
99 4DR auto Sportage, 30x950R15 tires, 3/4" strut spacer, rear air springs, Manual Hubs, FRONT Torsen LSD
00 Safari AWD, 2" lift, 30x9.50 tires, 4x4 conversion in progress
73 Pinzgauer Swiss Army troop carrier